The invention relates to a self-driving slipform paver comprising a machine frame carried by rolling assemblies and vertically adjustable by means of lifting columns. The invention further relates to a method for operating a self-driving slipform paver comprising a machine frame carried by rolling assemblies and vertically adjustable by means of lifting columns.
DE 1 99 57 048 A1 describes a self-driving slipform paver that comprises a machine frame carried by two front and two rear rolling assemblies in the form of track assemblies. Said rolling assemblies are in the form of drivable and steerable rolling assemblies, so the slipform paver is able to perform translational and/or rotational motions on the substrate. The slipform paver furthermore includes a device (hereinafter referred to as “slipform mould” or “concrete mold”) for shaping flowable material, in particular concrete. The slipform mould can be used to produce structures of varying design, for example protective concrete walls or water channels. The slipform mould is interchangeably secured to a support on the left or right side of the machine frame. The slipform paver further includes a control unit which is configured such that the velocities and the steering angles of the rolling assemblies are adjustable.
During operation, the slipform paver is intended to be controlled largely automatically and without significant interventions by the vehicle operator. When controlled automatically, the rolling assemblies are controlled in such a way that a reference point on the slipform paver or on the slipform mould will move along a predefined trajectory (target travel path), hence along the travel path or at a predefined spacing equidistant to said trajectory, in order to form a structure. The trajectory can in this case be described by individual segments which may comprise straight or curved lines.
One known method for controlling self-driving construction machines requires the use of a stringline in order to predefine the trajectory. The stringline is sensed by means of at least one sensor in order to be able to determine the position of the reference point on the slipform paver or on the slipform mould with reference to the stringline
Slipform pavers can also be controlled by means of a total station for determining position, or a GNSS (Global Navigation Satellite System). Data describing the trajectory are calculated for use in this automatic control. These data can be coordinates in a coordinate system that is independent of the slipform paver. Said data calculation can take place by means of a computer in an office away from the construction site, or it can take place on the machine. During operation of the slipform paver, a continuous comparison is being made between the actual position of the slipform paver, or rather the slipform mould, and the desired position, with the result that the slipform mould moves along said trajectory.
Successful production of monolithic concrete profiles requires the continuous feeding of concrete into the slipform mould. Conveying systems, for example belt conveyors or auger conveyors, are provided for feeding the concrete. The concrete is transferred into the slipform mould via a chute and a receiving hopper. The concrete is compacted inside of the slipform mould by means of vibrators. A large number of input parameters will be considered in order to successfully produce concrete profiles. The finished concrete profiles should be characterized by stability, close tolerances, and seamless transitions.
BRIEF SUMMARY
An object of the invention is to provide a slipform paver in which largely automatic control is adequate for satisfying the quality requirements demanded of the concrete profile. A further object of the invention is to specify a method for operating a slipform paver, said method being used to satisfy the quality requirements demanded of the concrete profile.
These objects are achieved according to the invention by way of the features of the independent claims. The dependent claims relate to advantageous embodiments of the invention.
The slipform paver according to the invention comprises a machine frame carried by at least three rolling assemblies and vertically adjustable by means of lifting columns, at least two of said rolling assemblies being drivable and at least one rolling assembly being a steerable rolling assembly, said slipform paver also comprising a support for a slipform mould that is arranged on the machine frame. The slipform paver furthermore comprises a control unit (as may also be referred to herein as a “controller”) for controlling the rolling assemblies that is configured in such a way that the velocities of the drivable rolling assemblies and the steering angle of the one steerable rolling assembly, or the steering angles of the steerable rolling assemblies, are adjustable.
Experience has shown that, particularly when following a curved path, the operation of a slipform paver places increased demands on the input parameter settings. In practice, when entering a curve from a straight section and when exiting a curve into a straight section, the vehicle operator is thereby required to make corrections to the predefined velocity of the slipform paver. Moreover, corrections are also necessary when the curvature of a curve changes, for example during the transition from a small curvature to a relatively large curvature, or vice versa.
The slipform paver according to the invention is characterized by a control unit which is configured such that, when the steering angle of the one steerable rolling assembly changes or the steering angles of the steerable rolling assemblies change, the velocities of the drivable rolling assemblies are adjusted so as to reduce the change in the velocity at which a reference point referring to the support for the slipform mould will move along a predefined trajectory, said change in velocity being caused by changing the steering angle. The control unit consequently counteracts any change in velocity of the reference point due to a curved path, thus making the movement of the slipform mould more uniform. The quality of the concrete profile produced by the slipform paver is improved as a result.
In this context, the term “reference point referring to the support for the slipform mould” is understood to mean a point of reference which determines the position of a reference point on the slipform mould mounted on the support. Said reference point can be located on the front or the rear (in the direction of work) of the slipform mould, or in the middle thereof. Preferably, the reference point will be assumed to be a point located on the longitudinal axis of the slipform mould, one preferably on the rear section of the slipform mould, hence at the outlet of the slipform mould. The reference point can also be located adjacent to the longitudinal axis of the slipform mould. This is particularly advantageous if the slipform mould has an asymmetrical cross-section in order to be able to produce a concrete component having an asymmetrical cross-section.
The control unit can be configured such that the velocities of the drivable rolling assemblies are adjusted such that the velocity at which a reference point referring to the support for the slipform mould is moving along a predefined trajectory will be maintained regardless of changes within a certain range to the steering angle of the steerable rolling assembly, or to the steering angles of the steerable rolling assemblies.
If a slipform mould is, for example, mounted on the right side (in the direction of work) of the machine frame of the slipform paver, and the slipform paver is moving along a straight path, then the velocity of a reference point located, for example, on the machine frame between the left rear rolling assembly and the right rear rolling assembly is equal to the velocity of a reference point located on the slipform mould that is situated on the right side of the machine frame. When entering a right hand curve, the velocity of the reference point located on the slipform mould decreases because said reference point is located on the inside of the curve. Consequently, the path velocity of this reference point is less than the desired velocity that was defined in advance for travel in a straight line. The result of this insufficient velocity is an excessive quantity of concrete exiting the slipform mould. Experience has shown that the concrete will ooze out from the bottom of the slipform mould or from the rear of the slipform mould, hence from either side of the mold outlet. Entering a left hand curve causes the path velocity of the reference point to be greater than the desired velocity that was defined in advance for travel in a straight line, as a result of which the previously formed concrete structure will be torn apart.
The control unit for the slipform paver according to the invention, or rather the operation of the slipform paver as per the method according to the invention, ensures that the velocity of the slipform mould when entering a curve and travelling through a curve will not change, or at least that it will not change as much as without the control unit according to the invention, with the result that the velocity will lie within a certain range still along a tolerable range. In thus referring to a “certain range,” this term can be understood to mean a range that lies between an upper limit and a lower limit. However, fixed limits need not be predefined for said control. So, in practice, the velocity of the reference point need not be constant, but can rather vary within certain boundaries.
Regardless of how the trajectory progresses, the control unit according to the invention permits the path velocity of the slipform mould to remain constant, or to at least remain within predefined boundaries, hence limiting, and preferably minimising, the change in velocity as a result of the curved path, thus making the movement of the slipform mould more uniform. Said velocity can be a velocity of the slipform paver that is predefined by the operator and ensures that the concrete profile satisfies quality requirements. Consequently, the transitional areas between straight and curved sections will not exhibit deficiencies in quality that are the result of excessive or insufficient speed.
A preferred embodiment of the slipform paver according to the invention provides a control unit which is configured such that the velocities of the rolling assemblies are adjusted such that a reference point referring to the support for the slipform mould will move along a predefined trajectory at a predefined reference velocity regardless of changes to the steering angle of the steerable rolling assembly, or the steering angles of the steerable rolling assemblies. This control concept permits the path velocity of the slipform mould to always remain constant, or at least largely constant, regardless of how the trajectory progresses. In practice, however, this manner of velocity control is not absolutely necessary. In practice, it may be sufficient for the control unit to be configured such that, when the direction of travel changes, the velocities of the rolling assemblies are decreased or increased according to the change in direction, hence only roughly adapting to how the path of travel progresses. The velocities of the rolling assemblies are adapted according to the change in the direction of travel, so the velocity is decreased or increased if the construction machine travels leftwards or rightwards. Depending on the degree to which the direction changes, hence the size of the steering angle, the velocity can be changed by a predefined amount, with the change in velocity increasing along with an increase in the steering angle. For example, correction factors with respect to the velocities of the rolling assemblies and depending on the change in direction as well as the amount the direction changes can be stored in a memory of the control unit. Said correction factors can be empirically determined during test drives.
In this context, the term “control” is understood to mean both control without feedback (open-loop) and control with feedback (closed-loop), in which the path velocity of the slipform mould, which must remain constant, is established as an actual value that is changed for a deviation from the desired target value (the reference velocity) so that the path velocity once again approaches the target value.
In a preferred embodiment of a slipform paver comprising a slipform mould arranged on the left side of the machine frame, the control unit is configured such that the velocities of the rolling assemblies are increased when transitioning from travel in a straight line to a left hand curve, and decreased when transitioning from travel in a straight line to a right hand curve.
In an alternative preferred embodiment of a slipform paver comprising a slipform mould arranged on the right side of the machine frame, the control unit is configured such that the velocities of the rolling assemblies are decreased when transitioning from travel in a straight line to a left hand curve, and increased when transitioning from travel in a straight line to a right hand curve.
In order to adjust the velocities of the rolling assemblies, the control unit can be configured such that the velocity at which the reference point referring to the support for the slipform mould will move along a predefined trajectory is determined according to the steering angle of the steerable rolling assembly, or the steering angles of the steerable rolling assemblies, because the steering angle determines the radius of the curve travelled. If the steering angle is equal to zero, which corresponds to travel in a straight line, no correction to the velocity predefined for travel in a straight line need be made in terms of increasing or reducing said velocity. Travel along a curve begins when the rolling assembly or rolling assemblies actuate. When the rolling assembly actuates or the rolling assemblies actuate, movement of the slipform paver is subject to the requirement that the steering angle not be changed along a circular path whose radius depends on the steering angle. The amount by which the path velocity of the reference point referring to the slipform mould must be increased or decreased in order to again correspond to the velocity predefined for travel in a straight line can then be calculated according to known geometric relationships with respect to the steering angle. The velocities of the rolling assemblies are then adjusted so that the reference point moves at the desired path velocity. It should in this context be recognized that the rolling assemblies on the outside of the curve must move at a higher velocity than the rolling assemblies on the inside of the curve.
An embodiment of the slipform paver according to the invention provides a control unit that comprises a memory in which a correction factor is stored with respect to at least one predefined steering angle value for the at least one steerable rolling assembly. The control unit is configured such that the velocities of the drivable rolling assemblies are corrected according to the correction factor, or rather according to the correction factors, hence being decreased or increased. The correction factors can be stored with respect to various steering angles in the form of a table, in which specific steering angle values are each assigned a correction factor. In this case, the sign of the correction factor can determine whether the velocity is decreased or increased for the relevant steering angle.
In a further preferred embodiment, the control unit is configured such that the steering angles of the steerable rolling assemblies are adjusted such that lines extended in a perpendicular direction from the axles situated on said steerable rolling assemblies will intersect at one point. This also applies to the positions of the non-steerable rolling assemblies. Adjusting the steering angle in this way is known as Ackermann steering. In Ackermann steering, the velocity at which the reference point referring to the support for the slipform mould is moving along a predefined trajectory can easily be calculated according to the steering angle of the rolling assemblies on the basis of the distance between the reference point and the center of the circle around which the rolling assemblies are moving in a circular path.
The slipform paver is provided with at least three rolling assemblies, in which case said one rolling assembly can be arranged at the front or at the rear (in the direction of work). In an embodiment comprising four rolling assemblies, the two front rolling assemblies can be steerable rolling assemblies, and the two rear rolling assemblies can be non-steerable rolling assemblies. In principle, however, all of the rolling assemblies can be steerable rolling assemblies, and all of the rolling assemblies can be drivable rolling assemblies. The drivable rolling assemblies can each comprise a drive motor, for example a hydraulic motor, and the drivable, steerable rolling assemblies can each comprise a drive motor and a steering actuator, for example a hydraulic steering actuator, in particular a piston-cylinder unit.
The control unit can comprise a sensing unit for sensing a stringline. In this embodiment, the control unit is configured such that the steerable rolling assembly is (or the steerable rolling assemblies are) controlled such that a reference point referring to the slipform paver will move along a predefined trajectory. The reference point referring to the slipform paver can be a reference point referring to the support for the slipform mould or the slipform moulds. Control units of this kind are conventionally known. As a result, the progress of the stringline determines the steering angle, which in turn determines the amount by which the velocity of the reference point referring to the support for the slipform mould, or rather the slipform moulds, is corrected, hence being increased or decreased, and will be reached by means of a corresponding increase or decrease in the velocities of the rolling assemblies.
An alternative embodiment provides that the control unit comprises at least one satellite navigation system receiver for receiving satellite signals from a global navigation satellite system. In this embodiment, the control unit is configured such that, based on the satellite signals, the position of a reference point referring to the slipform paver is determined in a coordinate system independent of the construction machine, and the control unit is configured such that the steerable rolling assembly or the steerable rolling assemblies are controlled such that the reference point referring to the slipform paver will move along a predefined trajectory. Control units of this kind are conventionally known. Since the satellite-based control is providing the relevant data regarding position and direction in a coordinate system, the velocity at which the reference point referring to the slipform mould is moving can be determined in addition to the associated path velocities of the rolling assemblies. Regarding velocity control, the velocity of the reference point referring to the support for the slipform mould, which is determined by means of the satellite navigation system, can be compared using a predefined reference value (target value) in order to adjust the velocities of the drivable rolling assemblies so that the actual value will approach the target value.
The control unit of the slipform paver according to the invention can comprise various components or assemblies for actuating the rolling assemblies, in particular drive motors or steering actuators. The control unit can be a part of a slipform paver central control unit, which runs a control program in order to control the drive motors or steering actuators of the rolling assemblies. For example, the control unit can include a Programmable Logic Control unit (PLC), which can comprise a micro-control unit that generates control signals for controlling the individual components.